The present invention is directed towards an apparatus for generating a belt tare compensation signal. More particularly, the present invention is directed towards an apparatus for generating a belt tare compensation signal which may be added or subtracted to the output of a load cell so that the resultant signal is a true indication of the weight of material on a belt feeder.
In various types of material feeders, for example, that disclosed in U.S. Pat. No. 3,724,720, the output of a load cell in operative contact with a conveyor belt feeder is utilized to control the batch size of material delivered by such conveyor systems. In the aforesaid patent, the belt tare is compensated for by a mechanically adjusted tare control which may be a zero adjust on a commercially available digital voltmeter. When using such control, the operator runs the belt feeder under no load conditions and visually adjusts the tare control so that the output of the voltmeter hovers around zero during the entire belt revolution.
While such a system provides a gross compensation for belt tare, variations in the thickness and density of the conveyor belt prevents such adjustments from providing an accurate count compensation for belt tare. Additionally, material deposited on the belt during operation of the conveyor feeder causes the accuracy of any mechanically adjusted signal to be temporary at best.
In an effort to overcome these and other disadvantages of such hand adjustments, the present invention provides an automatic circuit for generating a belt tare compensation signal which is representative of the average output of the load cell during a single non-loaded revolution of the conveyor belt. While such a system may be inaccurate for any single portion of the belt, these errors will be fully compensated for during any complete revolution of the belt.
Among the relevant prior art are U.S. Pat. Nos. 3,665,169 and 3,853,267.
For the purpose of illustrating the invention, there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangement and instrumentalities shown.